1. Field of the Invention
The invention relates to permanent magnet designs that can generate very strong and inhomogeneous fields primarily for NMR, MRI and MRT use.
2. Description of the Related Art
In Magnetic Resonance Imaging (MRI) there is a need for compact, very efficient and robust imaging systems that can perform high quality neurological MRI studies. Specifically, it is desirable for these systems to be capable of diffusion, angiography and functional imaging studies. MRI scanners typically work by manipulating hydrogen nuclei of patients inside a large, static and homogeneous magnet with radio frequency fields under the application of various encoding pulsed gradient magnetic fields. Today there is a need to add diffusion based MRI studies to quantify the development of stroke and to point to appropriate treatment planning. The use of strong gradients yields more informative diffusion weighted images. However, large switched gradient fields are practically difficult and there are physiological limits to the rate of change of magnetic fields.
Consequently, there is a dire need for high strength magnetic field gradients without requiring gradient switching. These new systems will enable improved diffusion imaging (essential for stroke studies), sharper angiography studies and potentially less noisy functional MRI studies. The invention will have strong, static gradients and thus yield more informative diffusion weighted images. Additionally, by taking advantage of a large static gradient in the main magnetic field the device will be compact and easier to site thereby enabling widespread use.